CN104838169B - Gear reducer with sealing plug providing axial support for gear backlash compensation spring - Google Patents

Abstract

The invention relates to a gear reducer (1) for a power steering module, comprising a housing (3), a worm (4) meshing with a worm wheel (6), and a spring (10) for actuating the gear, the spring (10) pressing the worm (4) radially against the worm wheel (6), away from an axis (XX ') of the worm, the wall of the housing (3) being bored, having an opening (14) blocked by a plug (15), the spring (10) for actuating the gear comprising at least one positioning flange (17, 18) projecting radially with respect to the axis (XX ') of the worm (4), a central portion (20) of the plug (15) having a guide wall (21) substantially transverse to the axis (XX ') of the worm (4), designed to be placed axially opposite said at least one positioning flange (17, 18) so as to prevent an axial displacement of the spring (10) beyond a predetermined functional stroke.

Description

Subtract with the gear for providing the sealing plug axially supported to gear clearance counterbalance spring Fast device

Technical field

The present invention relates to the general domains of power-assisted steering module (power assisted steering module), more Body, it is related to the gear reduction unit applied in this kind of module.

Background technique

It is known that especially in electronic supplementary module, there is the gear reduction unit including worm screw in power-assisted steering module, The worm screw is to be driven by stand-by motor and engaged on turbine, and turbine is coupled on the output shaft of power-assisted steering module.

In order to make up gear clearance (gear slack), and to limit parasitic noise, specifically, when by The gear deceleration When the torque of device transmission is lower, it is also known that power-assisted steering module shell and support worm screw one of bearing spider between be inserted into Spring, the spring is designed for radially pressing the worm screw against worm-gear toothing.

It may occur however that spring is displaced along worm axis particularly due to power-assisted steering module is vibrated, The degree of displacement is so that it can be observed that backlash compensation use scope is substantially reduced, therefore between gear piece and parasitic noise Impact occurs or is reinforced.

Summary of the invention

Therefore, it is an object of the invention to improve disadvantages mentioned above and propose a kind of design of gear speed reducer, with simple Persistently effective gear clearance compensation is provided with cheap mode.

The purpose of the present invention realizes that the gear reduction unit includes shell, worm screw, and worm screw is by extremely by gear reduction unit A few first bearing is engaged as described in being rotationally mounted to ball bearing in shell and with worm gear, and the gear reduction unit is also Including the gear clearance counterbalance spring being arranged between shell and first bearing, radially to press the worm screw against worm gear Gear piece, it is drilled in the wall of the extended line upper housing of the axis of worm screw, there is the opening that is blocked by plug, the gear reduction unit It is characterized in that the radial flange outstanding of axis that gear clearance counterbalance spring includes at least one relative to worm screw, also resides in plug Central part has the guiding wall for the axis for being generally transverse to worm screw, is designed to towards at least one described locating flange axis To placement, in this way mutually to be cooperated at least one described locating flange come to prevent the axial displacement of spring be more than pre- Determine function stroke.

Advantageously, the end wall of the use of plug, especially the center portion thereof point (hub) is used as maintaining backlash compensation bullet Spring is in the use of the axial stop of appropriate location, and the axial displacement for allowing to limit the spring is absolute function minimum value, because This prevents the spring axial dipole field, and its position is generally kept along worm screw, therefore in most in the case where all Excellent range of operation, in the range, the spring have good radial deformation amplitude relevant to enough rigidity, no matter its How is distortion level.

Stated differently, since of the invention, clearance compensating spring permanent retention is with enough stress ranks effectively to worm screw Force makes its radially ability closer to ground against worm gear, to prevent from easily generating any loose of impact and parasitic noise State.

It is and inessential but required it is apparent that plug is configured to generate certain axial gap in a manner of such Spring function axial stroke is corresponding (while being designed as preventing spring being more than the movement of the function axial stroke, as described above).

When temporal structure of the worm screw according to mechanical device and the manufacture and assembly in particular according to worm and worm wheel are public Difference etc., and when being intended to be moved to closer to worm gear rotary shaft or far from worm gear rotary shaft, such function axial gap will permit Perhaps the axial stroke element of mechanical device adjustment spring in the case where no blocking, the element are easy to the spring, bearing With the radial missing of worm screw.

Worm screw therefore be able to maintain with worm gear it is permanent it is prestressed contact, and thus worm and worm wheel rotation it is whole Optionally radial vibration in a looping fashion in a process.

Advantageously it is possible to the important cooperation range of the guiding wall mutually to cooperate with the locating flange of spring further allow to The spring is provided especially firm and is accurately guided, the radial position regardless of the spring and worm screw, or if there is If needing, regardless of the spring around the direction of the axis of the worm screw.

Advantageously, setting according to the present invention further allows using one and identical part (piece), such as fills in Son provides in others for closing shell and for keeping clearance compensating spring to be in position appropriate without necessity Between part so that the present invention has particularly simple, compact and light characteristic, and to implement the cost of the invention more It is low.

In addition, directly providing the clearance compensating spring with positionable wall by using plug, dimension chain is simplified, it is described Dimension chain defines the function axial gap for giving the spring by shell, associated with manufacture and build-up tolerance by limitation Error source, to allow mechanical device more accurate in the case where less cost.

Detailed description of the invention

On the other hand, it with reference to attached drawing, is provided for the purpose of description in a non-limiting manner and purely below by reading Description, other objects of the present invention, characteristics and advantages will be apparent, in which:

Fig. 1 global facility decomposition perspective view according to the present invention is shown according to the present invention for power-assisted steering module Retarder example.

Fig. 2 shows figure in the mid-plane of the clearance compensating spring of the axis perpendicular to worm screw according to partial sectional view The setting details of the intracorporal clearance compensating spring of the shell of 1 retarder.

Fig. 3 shows the setting details of the retarder of Fig. 1 and 2 according to the partial lengthwise sectional view of the axis according to worm screw.

Fig. 4 shows the variant of the clearance compensating spring used in the retarder of Fig. 1 to 3 according to overall perspective view.

Fig. 5 shows the variant of the plug used in the retarder of Fig. 1 to 3 according to overall perspective view.

Specific embodiment

The present invention relates to a kind of gear reduction unit 1, relates more specifically to a kind of gear suitable for power-assisted steering module 2 and subtract Fast device, the power-assisted steering module are used for the vehicle of auxiliary drive motor vehicle type.

In this respect, the gear reduction unit 1 will preferably be configured to transmit in a manner of such to be in Torque between 20N.m and 110N.m.

This is specifically illustrated in figures 1 and 3, gear reduction unit 1 include shell 3, such as by aluminium alloy or comprising There is the composite material of fiber-reinforced polymer-matrix matter to constitute.

Gear reduction unit 1 further includes worm screw 4, and the worm screw passes through at least one first bearing 5 such as ball bearing rotatably It is installed on the inside of the shell 3, and the worm and wheel 6 is meshed.

Typically, the rotary shaft (XX ') of worm screw overlaps and intersects with the rotary shaft (YY ') of turbine 6, and preferably Be mutually perpendicular to (although also consider other structures), by such mode, worm screw 4 in a manner of tangent line with 7 phase of gear piece of worm gear 6 Engagement is to drive worm gear.

Gear reduction unit 1 further includes the gear clearance counterbalance spring 10 that is inserted between shell 3 and first bearing 5 so as to diameter To ground pressing worm screw 4 against the gear piece 7 of worm gear 6.

It should be noted that unless otherwise indicated, " radial direction " either " radially " refer to be lateral one or other Direction, more specifically, the direction is essentially perpendicular to the rotary shaft (XX ') of worm screw 4, or even perpendicular to along about The distance of such orientation measurement of the axis.

Preferably, the spring 10 directly abuts shell 3, in recess, such as the set dug in the shell 3 (jacket) in, so that the spring can apply generally radially pre- restraining force on worm screw 4, which tends to The worm screw is pushed back backward towards the direction of the axis (YY ') of worm gear 6.

Advantageously, the formation of spring 10 (namely " disappears for compensating the operating clearance counterbalance spring in gap between gear piece Gap or anti-rebound " spring), by maintaining the contact between worm screw 4 and the gear piece 7 of worm gear 6 to improve the quality of engagement.

For this purpose, worm screw 4 and first bearing 5 form the element being moveably mounted relative to shell 3, the element is also by bullet The restoring force that spring 10 applies.

The radial stroke of displaceable element 4,5 allows the moving element to adjust the change that contact configures in which will be apparent from enough Change, the variation is particularly due to the geometrical defect of component or accessory, abrasion or differential thermal enlargement phenomenon.

For this purpose, worm screw 4 can be specifically in worm screw 4 and the worm screw end that is carried by globe joint type first bearing 5 Opposite end, carried by the second bearing 11 of globe joint type, and worm screw 4 passes through the Elastic Coupling of elastic claw type Part 13 is coupled on stand-by motor 12, as shown in Figure 1.

According to the present invention, on the extended line of the axis (XX ') of worm screw 4, the wall of shell 3 is drilled, and opening 14 is by plug 15 Closing.

Under particularly preferred mode, opening 14 will form entrance, and the entrance design is at for allowing at least first Bearing 5 and/or the even worm screw 4 of spring 10 enter shell 3 and are installed in the shell 3.

The opening 14 can also during attended operation use, such as to guide draining or on the contrary in order to moisten The introducing of lubrication prescription (such as grease).

During operation after the assembly is completed, plug 15 will advantageously ensure that the sealing of shell 3, more specifically, with respect to profit The sealing of lubrication prescription, dust, and/or water projection (projections of water).

According to the present invention, gear clearance counterbalance spring 10 include at least locating flange 16,17,18, locating flange relative to The axis (XX ') of worm screw 4 is radially projecting, and the central part 20 of plug 15 has the guidance for the axis (XX ') for being generally transverse to worm screw 4 Wall 21.

The guiding wall 21 be advantageously designed to it is axially placed towards at least one locating flange 16,17,18, by this method So as to which it is more than predetermined for being cooperated at least one described 16,17,18 phase of locating flange to prevent the axial displacement of spring 10 Function stroke.

Advantageously, guiding wall 21 is axially arranged with the scheduled function nominal range of one or more flanges, when described Flange 16,17,18 is during radial dynamic mobile along with the displaceable element formed by worm screw 4 and first bearing 5 to adapt to When gear clearance compensates, the functional distance is selected in a manner of such to form gap, the gap allows described convex enough The axial stroke (function stroke) of edge 16,17,18 and more fully all or part of spring 10.

However, by the direction of plug 15, relatively along the axial displacement of worm screw and the flange 16,17,18 The end of travel stop is erect, the functional distance will also be reduced enough to allow guiding wall 21 and 16,17,18 phase of flange Interaction, so that the end of the trip stop member can limit the axial stroke of the flange, to allow limited spring 10 Axial stroke is realized that the flange is fixed on spring within scheduled limitation range by the guiding wall 21.

Therefore, plug 15 is not only used as closing the component with seal casinghousing 3, also especially as designed for maintaining spring The 10 axial limitations in appropriate location, that is to say, that in axial position range, so that the spring is permanently tieed up on worm screw 4 Effective radial clearance compensation constraint is held, spring 10 has acceptable mechanical action on every of axial position range.

In this respect, the axial gap JA being formed between at least one locating flange 16,17,18 and guiding wall 21 is preferred Ground is less than or equal to 2mm, preferably lower than or equal to 1mm, even 0.8mm, is preferentially greater than or equal to 0.3mm, even 0.5mm。

Advantageously, according to dimension chain applicatory, by providing the nominal axial gap JA of non-zero, displaceable element 4,5 It is saved with the radial stroke ability of flange 16,17,18 in the case where not leaving extra axial space, for gear clearance This will be unfavorable for the stability and validity of compensation.

Under particularly preferential mode, guiding wall 21 is generally plane, and is preferably substantially perpendicular to snail The axis (XX ') of bar 4.

The guiding wall 21 is to preferably form the ramp radially slided, in being in contact with it, one or more flanges 16, it 17,18 can be compensated in moving process in gear clearance, the particularly buckling swing in its second bearing 11 when worm screw 4 When, it is radially slided in the case where not being obstructed,.

Guiding wall 21 preferably forms the solid core end wall of plug 15, is substantially located at the axis of the plug End, on the direction of worm screw 4, towards the inside of shell 3.

In addition, plug 15 preferably has the cylinder of rotation shown in Fig. 1,3 and 5, generating axis be will preferably correspond to The rotary shaft (XX ') of worm screw 4, and for ease of description, the axis (XX ') will be compared to.

Preferably, as shown in Figures 3 and 5, the central part 20 of plug 15 forms the solid cylinder of axial recess, wherein axial Guiding wall 21 is formed on the bottom of recess.

It the axially projecting end of flange 16,17,18 therefore can be adjacent inside recess.

The axial depth of the recess advantageously can be with corresponding to the height of the radial circular edge for delimiting the recess Axial gap JA as needed uses suitable depth according to other concrete condition, and particularly can be generally right It should be in the function axial gap JA between the axially projecting end and guiding wall 21 that flange 16,17,18 is arranged in.

In addition, as shown in Figures 3 and 5, plug 15 preferably has axial structure stage by stage comprising 20 He of central part Flange 22, the central part is towards spring 10, and the flange is towards the outside of shell 3, wherein (entire) of the flange 22 Diameter D22 is higher than the diameter of the central part 20, forms shoulder relative to the central part 20 with the flange (sholder) mode.

According to the preferred features that can be separately constructed invention, flange 22 forms elastic clip, and plug 15 is allowed to pass through loading (encasing) mode is fixed to shell 3.

According to the embodiment of variation, flange 22 can be integrally formed with central part 20, more specifically, flange shape by Polyamide or the hard plastics of polyformaldehyde (POM) type are formed, and shape and size will be suitable for so that the flange is same When with being arranged and maintained required resistance and elasticity in opening 14.

The elasticity of flange 22 can be improved in particular by circular reduction groove 23 is dug out, the groove and the method The edge of orchid 22 is coaxial, as shown in Figure 3.

The embodiment of another variation according to the present invention, flange 22 can be raw from the flexible plastic material of elastic type At for example, thermoplastic polyurethane, for example will be fixed to central part by overmolded or post forming (over molding) Divide on 20.

Advantageously, flange 22 will allow plug 15 to be rapidly and easily fixed on shell 3 by snap-fitted, more specifically Ground is fixed in groove 24, and outer in opening 14 is placed the groove on the wall of the shell 3 and dug out.

In this respect, it should be noted that opening 14 and plug 15 can be advantageously non-threaded, so that its manufacture is more Simply.

Preferably, central part 20 and possible flange 22 are made with single piece and by hard polymer material, hard The polyamide or polyformaldehyde of the preferred PA66 type of hard polymer material.

Therefore plug 15 can have monolithic core 20,22 made of hard plastic, in conjunction with slight, brightness and optimal resistance to Corrosion.

Such core 20,22 further for example will be particularly simple and fast by injection molding method or mechanical processing method manufacture Speed.

According to the embodiment of variation, central part 20 places the ring packing lining for being provided with flexible polymer material outside it (lining) 25, which preferably passes through overmolded manufacture.

Advantageously, 15 letter of plug will be allowed by manufacturing the application for the sealing lining for forming an entirety with plug 15 It is installed on shell 3 single, quick and renewablely.

Preferably, the sealing lining will be not only radially compressed against on central part 20, also by axially inclined against by flange 22 shoulders formed.Therefore, by a same pieces, it will ensure that particularly efficient radial and axial sealing.

The flexible polymeric material for constituting sealing lining 25 can be thermoplastic elastomer (TPE) (TPE) and in particular thermoplastic poly Amide (TPU).

By reference to central part 20, more specifically its hard portions (in addition to sealing lining 25), which can have, substantially exists Diameter (internal diameter for if any, corresponding to sealing lining 25) between 25mm and 33mm.

Sealing lining 25 can have the outer diameter generally between 35mm and 36mm, and the overall diameter D22 of flange 22 is generally Between 36mm and 38mm.

The rough thickness E 22 of flange 22 can weaken (axial direction) depth of groove 23 between 1mm and 2mm, if yes It can be between 0.5mm and 1.5mm.

As shown in figure 4, gear clearance counterbalance spring 10 preferably includes multiple locating flanges 16,17,18, preferably three Locating flange 16,17,18, is angularly distributed, is preferably angularly distributed every a certain distance, around the axis of worm screw 4 (XX '), and be designed to cooperate with 21 phase of guiding wall of plug 15.

Advantageously, the use for the several supporting-points being located remotely from each other, particularly form three supporting points three flanges 16, 17,18 use allows to obtain spring 10 against the steady of the guiding wall 21 for sliding flat contact surfaces type (plane in the plane) Fixed and balance support, unique plane (unique plane) (geometrically) pass through three supporting-points.

Such Dynamic link library in similar " perfection " flat contact surfaces preferably allows for displaceable element 4,5 and is embedded Flange 16,17,18 radially slided with the free function of very little friction, while preventing 10 axial dipole field of spring, or even prevent Spring is blocked relative to the inclination or possible friction of the axis (XX ') of worm screw 4.

Preferably, clearance compensating spring 10 includes annular blade 26, makes 26 quilt of blade in thickness direction around first bearing 5 (alternatively, more fully, being designed as being wound on coil) is wound on coil.

Advantageously, therefore one or more locating flanges 16,17,18 can be formed by earflap (tabs), the earflap and The edge of the blade 26 is integrally formed and radial folding.

Such spring can be manufactured in a simple manner, cutting and folding based on identical strap (ribbon sheet) It folds, preferably metal.

Furthermore tangent (secant) is advantageously tilted in the locating flange 16,17,18 of blade 26, by this method so as to substantially On follow imaginary conical big envelope.

In this respect, locating flange 16,17,18 will preferably have axially extending element (towards the outside of spring 10, On the direction of plug 15) and radially extension element (towards axis (XX ')), the radially extension element preferentially occupies the majority, that is, It says more important than axially extending element.

Preferably, it is turned to by being formed substantially around the bearing 5, blade 26 will angularly cover first bearing 5 Major part or even almost all, the particularly outer ring of ball bearing.

Preferably, as shown in Figures 2 to 4, clearance compensating spring 10 includes heel shape object (heel) 27, and the heel shape object 27 is from the One bearing, 5 radial deflection engages in the groove 30 being formed in shell 3, is preferably parallel to axis (XX '), therefore to hinder The spring 10 is kept off around the rotation of the axis (XX ') of worm screw 4.

The heel shape object 27 forms outer radial and protrudes, and indicates the arranged radially noncontinuity relative to 26 part of blade, The curvature of this and first bearing 5 is well suited for.

Advantageously, the heel shape object 27 is flexibly against the bottom of groove 30, so as to which diameter is created and applied to bearing 5 It is limited to backlash compensation, so that the limitation is created and applied to worm screw 4.

For this purpose, heel shape object 27 advantageously can generally be bent into U-shaped to form stirrup shape part (stirrup), radially It highlights from blade 26 and bearing 5, wherein the bottom of the outside rear abutment groove 30 of the diameter of the stirrup shape part.

Advantageously, it is hereby ensured that radial compression worm screw 4 and the double actions for inhibiting spring 10 to rotate for heel shape object 27.

Preferably, heel shape object 27 and blade 26 form an entirety, and the heel shape object, which preferably comprises, extremely to be extended.

In this respect, it should be noted that heel shape object 27 can advantageously be rived, transverse to axis (XX '), such as Fig. 3 and 4 Shown, more specific to be made of side by side ground the axial direction at 26 both ends of blade, blade angularly covers the circle of spring 10 of a part Week.

Each end has the width (axial range) below or equal to blade half width (axial range) thus, together When blade width can in addition be essentially equal to first bearing 5 width (axial range).

Advantageously, such spring 10 that open deformable coil is integrally formed in the overall situation is arranged, it is ensured that resilient suspension Elasticity, balance and robustness, the resilient suspension guarantee gear clearance compensation.This also allows simply to be manufactured.

As shown in Fig. 1 to 3, spring 10 advantageously will be freely engaged in the outer rim of first bearing 5, is more specifically engaged in On the radially outer edge of ball bearing outer race, the axis of the spring 10 further preferably axis with worm screw 4 and/or bearing 5 (XX ') is consistent.

Under especially preferential mode, one or more locating flanges 16,17,18 form one or more two-way positioning Component is arranged so as on the one hand cooperate with 5 phase of first bearing, to stop spring 10 towards gear area in a manner of such Axial translation on the first direction in domain, worm screw 4 is in contact with worm gear 6 on the gear region, on the other hand with plug 15 The cooperation of 21 phase of guiding wall, to stop the translation of spring 10 in a second direction that is opposite the first direction, that is, to Stop translation of the spring 10 on the direction of plug 15 outside shell 3.

Axially maintain identical locating flange 16 between the edge of first bearing 5 and guiding wall 21 on part, 17, 18, therefore can ensure axially maintaining for both direction upper spring simultaneously, so that it is guaranteed that by simple and compact installation, with low Cost is axially maintained spring under very effective mode.

Present invention notably relates to a kind of power-assisted steering modules 2, are provided with gear reduction unit 1 according to the present invention, tooth The worm screw 4 of wheel decelerator is (shown in the point as shown in figure 1) driven as electric servo-motor 12, and the worm gear 6 of gear reduction unit designs To apply auxiliary torque on the driven shaft 31 for coupling with turning-bar or steering rack according to scheduled auxiliary regular.

Under preferred mode, driven shaft 31 will carry the pinion gear 32 for being used to be engaged on steering rack (not shown), Its azimuthal orientation for being translated across the track rod control vehicle guide wheel being connected in short axle.

The invention further relates to a kind of steering systems and vehicle for being equipped with power-assisted steering module 2 according to the present invention, more In particular it relates to a kind of for example for transporting the motor vehicles of the wheel type of individual or commodity, it is equipped with such steering system System.

Present invention finally relates to a kind of plug 15, the plug be made of plastic material, and be used for power-assisted steering The shell 3 of module 2,15 one side of plug includes core 20,22 made of hard plastics, and the core is with single piece Solid core 20 is formed, the guiding wall 21 of general planar and generation axis (XX ') perpendicular to the plug is provided, And flange 22 is formed, which illustrates the diameter relative to the central part 20 on the axial distance for leaving guiding wall 21 Outside shoulder is formed simultaneously elastic fixing clip, on the other hand the plug includes the ring packing lining 25 being made of elastomer, should Sealing lining preferably passes through overmolded increase and is fixed on the core 20,22, by this method to surround central part 20 Periphery.

Advantageously, such plug 15 will have multiple functions, and shell 3 is fixed in a manner of being inserted into shell at its own On ensure the sealing of the shell 3, and the axial stroke of gear clearance counterbalance spring 10 is controlled, since guiding wall 21 is realized One of function axial direction travel limit range of spring 10, to prevent the spring 10 from moving axially beyond the function row Journey.

The integrally production in one or several plastic materials of plug 15 may be with fiber-reinforced polymer-matrix matter Laminating production will advantageously further ensure the slight of plug 15, brightness and corrosion resistance.

Central part 20 can be further recessed, as described above.

Obviously, the present invention is not limited in embodiment described above, and those skilled in the art is particularly capable of independence Or freely combine feature as described above in one and/or another.

Claims (20)

1. A gear reducer (1), comprising a housing (3) and a worm (4), the worm being rotatably mounted in the housing (3) through at least one first bearing (5), and the The worm (4) meshes with the worm wheel (6), and the gear reducer further includes a gear gap compensation spring (10) arranged between the housing (3) and the first bearing (5), so as to radially press the Said worm (4) abuts the toothed plate (7) of the worm wheel (6), the wall of the housing (3) is drilled on the extension of the shaft (XX') of the worm, with an opening blocked by a plug (15) (14), the gear reducer (1) is characterized in that the gear backlash compensation spring (10) comprises at least one positioning flange (16, 17, 18) that protrudes radially with respect to the axis (XX') of the worm (4) ), said gear reducer (1) is also characterized in that the central part (20) of the plug (15) has a guide wall (21) substantially transverse to the axis (XX') of the worm (4), which is designed as placed axially facing said at least one locating flange (16, 17, 18) in such a way as to prevent the axial direction of the spring (10) in cooperation with said at least one locating flange (16, 17, 18) displacement beyond a predetermined functional stroke; wherein the central portion (20) forms an axially recessed solid cylinder, wherein the bottom of the axial recess in said cylinder forms a guide wall (21) for at least one positioning flange (16, 17) , 18) can adjoin the guide wall (21) inside the recess. 2. The gear reducer according to claim 1, wherein the first bearing (5) is a ball bearing. 3. Gear reducer according to claim 1 or 2, characterized in that the axial clearance (J _A ) formed between the at least one positioning flange (16, 17, 18) and the guide wall (21) is low 2mm or more and 0.3mm or more. 4. The gear reducer according to claim 3, characterized in that the axial clearance (J _A ) is lower than or equal to 1 mm and higher than or equal to 0.5 mm. 5. The gear reducer according to claim 4, characterized in that the axial clearance (J _A ) is lower than or equal to 0.8 mm and higher than or equal to 0.5 mm. 6. Gear reducer according to claim 1 or 2, characterized in that an annular sealing liner (25) of flexible polymer material is provided on the periphery of the central portion (20). 7. The gear reducer of claim 6, wherein the annular sealing liner is manufactured by overmolding. 8. Gear reducer according to claim 1 or 2, characterized in that the central part (20) and the flange (22) are made of a polymer material in one piece. 9. The gear reducer according to claim 8, wherein the polymer material is polyamide or polyoxymethylene of the type PA66. 10. The gear reducer according to claim 1 or 2, characterized in that the gear backlash compensation spring (10) comprises a plurality of positioning flanges (16, 17, 18), a plurality of positioning flanges (16, 17, 18) Distributed angularly around the axis (XX') of the worm (4) and designed to cooperate with the guide wall (21) of the plug (15). 11. Gear reducer according to claim 10, characterized in that the positioning flanges (16, 17, 18) are angularly distributed around the axis (XX') of the worm (4) at regular intervals. 12. The gear reducer of claim 10, wherein the plurality of positioning flanges (16, 17, 18) includes three positioning flanges (16, 17, 18). 13. A gear reducer according to claim 1 or 2, characterized in that one or more positioning flanges (16, 17, 18) form one or more bidirectional positioning members, arranged in such a way as to be able to interact with the first A bearing (5) cooperates to block the axial translation of the spring (10) in the first direction towards the gear region where the worm (4) is in contact with the worm wheel (6) and on the other hand with the worm wheel (6) The guide walls (21) of the plug (15) cooperate to block the translation of the spring (10) in a second direction opposite to the first direction. 14. The gear reducer according to claim 1 or 2, characterized in that the clearance compensation spring (10) comprises an annular blade (26) which is wound into a coil in the thickness direction around the first bearing (5) , one or more locating flanges (16, 17, 18) are formed by lugs integrally formed with the edge of said annular blade (26) and folded radially. 15. Gear reducer according to claim 1 or 2, characterized in that the backlash compensation spring (10) comprises a heel (27) radially from the first bearing (5) Offset, engages in a groove (30) formed in the housing (3) so as to block the rotation of the spring (10) about the axis (XX') of the worm (4). 16. Gear reducer according to claim 1 or 2, characterised in that the plug (15) has an axially staged structure comprising a central part (20) and a flange (22), the central part oriented towards Spring (10), said flange facing the outside of the housing (3), wherein the diameter (D22) of said flange (22) forms a shoulder with respect to said central portion (20) ) is larger than the diameter of the central portion (20). 17. Gear reducer according to claim 16, characterized in that the flange (22) forms a spring clip allowing the plug (15) to be fixed to the housing (3) by means of fitting. 18. The gear reducer of claim 3, wherein the central portion (20) has an edge delimiting the recess and the axial depth of the recess corresponding to the height of the edge corresponds to the axial clearance (J _A ). 19. A power steering module (2) provided with a gear reducer (1) according to any one of the preceding claims, the worm (4) of which is driven by an electric auxiliary motor (12), The worm gear (6) of the gear reducer is designed to exert an auxiliary torque on the driven shaft (31) for coupling with the steering rod or steering rack. 20. A method comprising using a plug (15) as an axial stop to maintain a gear backlash compensation spring (10) in place within a gear reducer (1) comprising: housing (3), a worm (4) rotatably mounted within the housing by at least one first bearing (5) and which meshes with a worm wheel (6), and Wherein the gear clearance compensation spring (10) is arranged between the housing (3) and the first bearing (5), so as to radially press the worm (4) against the tooth piece of the worm wheel (6), wherein the wall of the housing (3) is drilled on the extension of the shaft (XX') of the worm, with an opening (14) blocked by a plug (15) having a central portion (20), wherein the gear backlash compensation spring (10) comprises at least one locating flange (16, 17, 18) protruding radially with respect to the shaft (XX') of the worm, and wherein the central portion (20) of the plug (15) ) has a guide wall (21) substantially transverse to the axis (XX') of the worm, and wherein said guide wall (21) is placed axially facing said at least one locating flange (16, 17, 18) in such a way as to communicate with said at least one locating flange (16, 17, 18) cooperate so that said at least one locating flange (16, 17, 18) and said gear play compensation spring (10) are axially supported against said guide wall (21), thus allowing said locating flange ( 16, 17, 18) and the backlash compensation spring (10) are free to slide radially against the guide wall (21) while preventing axial displacement of the backlash compensation spring (10) beyond the guide wall (21); wherein the central portion (20) forms an axially recessed solid cylinder, wherein the bottom of the axial recess in said cylinder forms a guide wall (21) for at least one positioning flange (16, 17, 18) Can abut the guide wall (21) inside the recess.